<div id="editer" contentEditable="true" style="border:1px solid #ccc;width:400px;height:200px" >
     123456<br/>123456
     </div>
     <button onclick="InsertImage()">InsertImage</button> 
 <script language="javascript">
 var editer=document.getElementById('editer');
 function InsertImage(){
    ImagePath = window.prompt('ͼƬURL:', '');
    editer.focus();
    document.execCommand('InsertImage', false, ImagePath);
 }
</script>